Decline in kidney function before and after nephrology referral and the effect on survival in moderate to advanced chronic kidney disease.

BACKGROUND: The burden of chronic kidney disease (CKD) is high, but its natural history and the benefit of routine nephrology care is unclear. This study investigated the decline in kidney function prior to and following nephrology referral and its association with mortality.

METHODS: This study provides a retrospective review of the individual rates of glomerular filtration rate (GFR) decline (millilitre per minute per 1.73 m(2)/year) for the 5 years before and after referral in 726 new referrals with stages 3-5 CKD to one renal unit between 1997 and 2003. Blood pressures are averages at referral, 1 and 3 years post referral. Logistic regression and Cox's models tested factors predicting post-referral GFR decline and the impact on mortality.

RESULTS: Mean (SD) age was 72 (14), and 389 (54%) patients had stages 4-5 CKD. GFR decline slowed significantly from -5.4 ml/min/1.73 m(2)/year (-13. to -2) before to -0.35 ml/min/1.73 m(2)/year (-3 to +3) after referral (P < 0.001). Blood pressure also reduced significantly (155/84 to 149/80, P < 0.05) with most changes occurring within 1 year of referral. Factors predicting a non-progressive post-referral decline included a lower systolic blood pressure at referral and 1 year after referral, a CKD diagnosis other than diabetic nephropathy, less baseline proteinuria and a non-progressive pre-referral GFR decline. A non-progressive post-referral GFR decline was independently associated with significantly better survival (hazard ratio 0.55, 95% CI 0.40-0.75, P <or = 0.001) after adjustment for known risk factors.

CONCLUSIONS: Following nephrology referral, GFR decline slowed significantly and was associated with better survival. Earlier detection of patients with progressive CKD and interventions to slow progression may have benefits on both kidney and patient survival.